The objectivs of this research proposal are to develop a comprehensive basis for understanding porcelain-metal bonding and thermal compatibility, and to apply this new information toward producing a successful system for restorative dentistry: Knowledge gained will provide a new understanding of the physics and engineering principles involved in the construction of porcelain-fused-to-metal restorations. Dental health care will be improved by providing a functional system that can be used with confidence by the dental profession without increasing costs for patient care. This investigation, through learning of the role of oxide adherence in porcelain-metal bonding and how to control and measure properties of porcelain at the very high rates of cooling encountered in the dental laboratory, will make possible important gains in understanding the scientific basis for this important area of research and will be found of value throughout modern glass industry. It appears from our current research that an external, adherent oxide is an indispensable requirement for the formation of a durable porcelain-metal bond. To develop a comprehensive basis for the understanding of porcelain-metal bonding, the nature of oxide adherence and growth mechanisms must be understood. The specific aims addressed to these areas of investigation are to evaluate the role of oxide adherence in porcelain bonding for a wide variety of commercial and experimental alloys, to contribute to the understanding of oxide adherence mechanisms, and to study the transition from complete internal to external oxidation. In addition, the mechanism and effects of internal oxidation of Pd-ag alloys, particularly with regard to porcelain discoloration, will be investigated. In order to assure thermal compatibility in a new porcelain-metal system, the role of thermal properties of the porcelain cooled at high rates in the dental fabrication process must be understood. The specific aims to gain this understanding are to determine the transition temperature (Tg), setting temperature (Ts), thermal expansion and viscosity for heating and cooling rates between 10 C/Min and 500 C/Min, to use these data in mathematical models for calculating stresses which arise from thermal incompatibility, and to evaluate these models by comparison of the predicted deformation of a composite beam with that observed experimentally. The permissible limits of thermal compatibility imposed upon the system by porcelain composition will be evaluated by studying the interaction between the adherence of the metal oxide (the primary adherence factor) and thermal compatibility.